Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 302035
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
335 PM CDT MON MAY 30 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 335 PM CDT Mon May 30 2016

Awaiting development in our forecast area this afternoon, and
monitoring two areas for possible development. First would be in
northwest Iowa, where some elevated showers or storms could work
northward through far eastern Nebraska and far western Iowa. Main
concern for this area would be brief gusty winds due to a deep dry
sub-cloud layer, though with fairly weak winds throughout the
profile, most likely winds would remain sub-severe.

Main focus will be with storms now developing in central South
Dakota and north central Nebraska. High-res CAMs have been fairly
consistent showing this activity continuing to expand in coverage
through the late afternoon/evening as upper wave moves out of the
Northern Rockies. Initially expect to be looking at discrete cells
capable of strong wind gusts and moderate hail, most likely reaching
western portions of Brule/Gregory counties after 6 pm. This activity
should then develop into more of a linear cluster of cells as it
pushes east across southeast South Dakota. As the storms work into
area of weaker shear, expect hail threat will begin to diminish.
However, soundings still showing dry mid levels which could result
in continued strong wind threat as the storms approach I-29 after
9-10 pm.

Most of the storms should exit southwest Minnesota/northwest Iowa
prior to 12Z Tuesday. However, boundary does slow a bit late tonight
into tomorrow morning, with lingering instability in areas southeast
of Highway 60 into the afternoon. Will hang onto some chance pops in
these areas through the morning, gradually decreasing through the
afternoon as boundary washes out and deeper dry air takes over in
mixy westerly flow.


.LONG TERM...(Tuesday night through Monday)
Issued at 335 PM CDT Mon May 30 2016

Zonal flow is expected to prevail through the first half of the
extended leading to near normal temperatures and a few instances for
the threat of thunderstorms.  Tuesday night upper low scoots by to
the north resulting in a few clouds across the highway 14 corridor,
but otherwise expect ok radiative conditions.  Northwesterly winds
developing along with the cold air advection will result in winds
hanging around 10 mph much of the night keeping the atmosphere quasi-
mixed.

Breezy northwest winds are expected to develop on Wednesday. Expect
a fairly healthy cumulus deck to develop across the area, with a
small amount of instability across southwest Minnesota. Did not
include mention of pops however with dry subcloud layer...limited
instability and lack of trigger beyond diurnal heating.

Better radiative conditions expected Wednesday night across the
forecast area and have trended towards the cooler guidance values.

Thursday is somewhat tricky as models suggest convective potential
across the south. Steep lapse rates in the 750-700 mb layer suggests
the potential of some isolated elevated convection developing along
the Missouri River Valley.  How far east and how widespread it is
still questionable though as there is little in the way of forcing
beyond mid level warm air/theta-e advection. Given it is
questionable, have left pops out for now, but afternoon looks
conditional if we can destabilize enough.  Again, suffering from a
lack of a strong trigger so kept afternoon pops to slight chance
mention for now.

A much strong mid level wave drops southeast across the upper
Midwest on Friday. Models are debating on how strong this feature
is.  The ECMWF is weaker with the wave, and keep it mainly across
central Minnesota, while the GFS is stronger and brings the southern
portion of the wave across southwest Minnesota.  Left chance pops
for this fattier, but will likely have to refine once trajectory
becomes more clear.

Thereafter...upper ridge across the western US begins to build into
the region leading to generally dry and seasonal temperatures next
weekend.


&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1243 PM CDT Mon May 30 2016

Quiet start to this TAF period should become more active from late
afternoon through the overnight hours. Scattered showers or storms
may develop in northwest Iowa after 20Z. Storms appear more likely
east of KSUX, and thus have not included this in the KSUX TAF.
Isolated wind gusts over 35kt possible with this activity.

Somewhat more organized line of storms expected to move east
across the forecast area after 31/00Z, reaching I-29 corridor
between 03Z-06Z and exiting east of Highway 71 by 12Z. Localized
MVFR conditions and wind gusts over 35kt may be associated with
this line, more likely west of I-29 corridor.


&&

.FSD Watches/Warnings/Advisories...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...JH
LONG TERM...BT
AVIATION...JH



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